This invention relates generally to devices which support various surveying and geomatics poles, and more particularly to a support suitable for steading poles during measurements, permitting calibration verification of leveling indication vials, and holding a portion of the pole out of contact with the ground.
During a typical survey, multiple and various measurements are often taken requiring varies degrees of accuracies. For example, measurements of property boundaries may require a greater degree of accuracy than measurements locating the position of fire hydrants, yet both measurements may be performed in the same survey using the same geomatics target device. In order to meet the specific accuracy or speed efficiency requirements of a particular measurement, survey crew members may be required to change the support holding a geomatics target device. The target devices include prismatic retroreflectors, global positioning system receivers and optical targets.
Commonly, various types of geomatics poles are used to support geomatic target devices. These geomatics poles typically are fitted with a ground engaging point on a base end, permitting precise indication of a ground point. To provide desired line of sight clearances, the target device is typically located on the apex of the pole, opposite of the base end. A level indication vial is commonly located at a point along the length of the pole to facilitate vertical collimation of the pole over the ground point in a process known as plumbing. Geomatics poles, which may be either fixed length or telescopic, are capable of retaining an established length throughout multiple measurements. Known and constant target heights save measurement calculation time. As a result, measurements can be obtained much faster with geomatics poles than with other supporting devices, such as tripods.
However, geomatics poles have several disadvantages. For one, the level indication vials of these poles often lose their accuracy calibration, which may cause inaccurate measurements. Because of this deficiency, level vial accuracy must be verified periodically. Many prior art level vial checking devices are dedicated only to the function of checking level vials and require being fixed to a wall. Thus, these wall mounted level vial checking devices are not available for use in the field.
For some measurements, geomatics poles may be handheld in vertical collimation over a ground point. Positioning a geomatics pole positioning by hand provides a fast and convenient method of taking measurements. However, the practice of handheld positioning of geomatics poles also has disadvantages. One of these disadvantages is that precise and extended retention of pole position is very difficult. Therefore, measurements taken with handheld poles are less precise than supported ones. Another disadvantage with handheld poles becomes evident when a surveyor must perform a task not involving the pole, such as installing a monument or making a note. In these instances, the pole is often laid directly on the ground, subjecting the pole and target to damage and malfunction as a result of ground borne debris (e.g., sand, mud).
A number of dedicated prior art devices are offered to steady or support geomatics poles, which permit more precise measurement observations to be taken. Many of these prior art pole support devices provide supporting legs in the form of bipods or tripods. One version of a geomatics pole supporting bipod is illustrated in U.S. Pat. No. 3,570,130 to Boehm. A version of a dedicated geomatics pole tripod is illustrated in U.S. Pat. No. 5,749,549 to Ashjaee. These pole support devices have disadvantages, among which is that they only perform one function.
In some instances, tripod stands, which are typically designed to support primary instruments such as transits, theodolites and total stations, are also used to support geomatics targets. In other instances, dedicated target support tripods are used. One version of a dedicated target support tripod is illustrated in U.S. Pat. No. 3,195,234 to Glidden. While the tripods are quite stable, they also have a number of disadvantages. For instance, in the case of instrumentation tripods, adaptors (commonly known as tribrachs) are required to provide a connective interface between the target and the tripod. Additionally, these tripods are slow and difficult to set up with targets because the procedures for establishing precise vertical collimation, and determination of height of targets, are quite time consuming. Dedicated target tripods have an additional disadvantage of performing only one function. The disadvantages of using tripods for geomatic target supports often limit their use to those measurements requiring great accuracy.
Standard (i.e., nondedicated) tripods may be adapted to support geomatics poles so that the target devices can remain on the poles, a practice which saves time. One prior art surveying tripod type pole support device is illustrated in U.S. Pat. No. 4,290,207 to Browning. These types of support devices also have many disadvantages, such as being capable of only one use; providing a pole to tripod interface. Also, the positive coupling connections found in many of these pole supports tend to inhibit free rotation of the poles, which inhibits level vial calibration confirmations. These positive connections also resist sliding the support along the pole thereby resisting gravitational forces on the pole and limiting bearing support of the point on the ground surface. Additionally, these pole supports tend to be complex in design, heavy, and expensive.
One prior art tripod type geomatics pole support, marketed under the name Hold A Pole, permits free rotation, and free sliding of the geomatics pole. However, this pole support also has disadvantages, one of which is that the captivity of the geomatics pole is rather flimsy, as the pole is retained with an elastic band. Additionally, the elastic band must be manually attached and detached when the geomatics pole is installed and removed, which is inconvenient and also requires two hands to perform. Additionally, in order to prevent friction and thus permit free sliding and rotation of the pole, the elastic band must be rather weak in design, which may cause the pole to be unstable and possibly result in inaccurate measurements. Additionally, the force of wind can critically load the elastic band allowing the geomatics pole to fall to the ground thereby subjecting the pole, the level vial and its geomatics target to damage.
In addition to taking measurements, persons performing surveys must also engage in other activities such as installing monuments or making notes. In order to free surveyors hands while engaged in activities other than measuring, geomatics equipment is often placed directly on the surface of the ground. The exposure of survey equipment to ground borne debris such as mud or sand can render the equipment inaccurate or even inoperable. Moreover, field conditions in surveying often include rough and remote terrains, and surveying equipment must often be transported by hand, so features of weight and convenience have particular importance to surveyors.